You go to, say, net.admin.net-abuse.email, a newsgroup you occasionally read. You look at the various technical posts and whinges. Then you read something totally ridiculous -- say some spammer is threateneing to sue not just an individual for blackholing him, but their ISP, SPEWS, anyone who uses SPEWS as a blocklist, and USENET itself.*

That's it, too much. Someone is trying to sue a protocol, for fuck's sake. You snort in a mixture of amusement and disgust. But it's all gone terribly wrong. Your snort coincided with a sip of coffee, and now you've spat it all over your keyboard, ruining it. And your cat was so frightened by your reaction that it's jumped off your lap, scratching you on the way down, and is cowering in a corner.

[common, esp. on news.admin.net-abuse.email] Contraction of "Coffee & Cats". This frequently occurs as a warning label on USENET posts that are likely to cause you to snarf coffee onto your keyboard and startle the cat off your lap.